Stabilized petroleum oils



ployed with the refined oil.

. oleaginous material toward oxidation.

is to provide processes for the preparation of the oil STABILIZED PETROLEUM OILS No Drawing. Application July 15, 1954 Serial No. 443,718

16 Claims. (Cl. 196-52) .This invention relates to the preparation of an improved oxidation inhibitor for petroleum oils, and to stabilized oil compositions containing a minor proportion of the inhibitor.

Petroleum oils, especially petroleum oils that have been highly refined by chemical means, tend to absorb and reactwith oxygen. This reaction is accelerated by the elevated temperatures and metal contact often em- For example, treatment of a light lubricating oilv with sulfuric acid, hydrofluoric acid, aluminum chloride, furfural, sulfur dioxide or the like, yields a highly refined oil having desirable properties, but which readily reacts with oxygen to form deleterious materials.

Various materials have heretofore been described as additives for petroleum oils, one or several properties of the oil being enhanced by relatively small quantities 1 thereof. For example, the use of relatively high molecular Weight fractions from petroleum operations, such as the residue from thermal cracking, as an additive for lubricating oils has been taught. Prior to incorporation in the oil, the additive may be subjected to a refining operation, such as hydrogenation or treating with an acid. Generally the purpose of such additives is to improve the color and bloom of the lubricating oil. While such additives have been described as successful in improving the color and bloom of lubricating oil, they have not been successful in providing an oxidation inhibitorwhich is effective in increasing the resistance of unstable oils toward oxidation. In some instances a. multiplicity of'additives have been employed in an attempt to prepare a stable oil.

An object of the invention is to provide a novel oil additive elfective for increasing the resistance of an Another object additive of the invention. A further object is to provide a stable oil composition comprising an oil unstable toward oxidation and a stabilizing quantity of a novel oxidation inhibitor.

It has now been foundthat by subjecting a hydrocarbon fraction from a catalytically cracked petroleum oil, the components of which have molecular weights within a specific range, to certain treating steps, as here inafter described, an oil additive remarkably effective, when incorporated in minor amounts in an unstable oil, for increasing the resistance of the oil to oxidation is obtained. While it is not desired to be limited by theoretical considerations, it is believed the elfective constituents 'of the additive are polynuclear aromatic hydrocarbons having molecular weights within a rather narrow range, and that the specific treating steps employed in the present invention remove materials that exert a deleterious effect on the final oil composition. Good results are obtained, in accordance with the invention, when oleaginous materials-that are susceptible cl States Paten t iO to oxidation are employed as the preponderant component I of the compositions of the invention. Oils that have been ceptible to oxidation and give excellent results in the present invention. It is preferred to employ oilsof petroleum origin that have been refined by chemical means, and good results are obtained therewith, but synthetic oleaginous materials that are susceptible to oxidation, .such as polyethylene oxide, also give'good results; j

As more fully described hereinafter, it is essential to the success of the invention that theadditive be prepared from a catalytically cracked oil. From example, a fraction of comparable molecular weight range from a thermally cracked oil exhibits deleterious, rather than beneficial, effects when incorporated in an unstable oil. However, a thermally cracked or otherwise treated oil can be used so long as catalytic cracking is the last opmospheric to 500p. s. i. g. and spacerates of from 0.1 to 10 volumes of oil per volume of catalyst per hour. F

It is also essential that the porition of the cracked oil employed, hereinafter "defined, be subjected to specific treating steps. If the treating be omitted,

an additive effective to an extent toward oxidation inhibition is obtained, but it is inoperative in the invention because of color: deterioration of the oil composition and of the additive itself when stored for an appreciable time. It islfurther essential that the components of the fraction-from the catalytically cracked oil have molecular weights within the range of from 200 to, 400. This fraction may boil within diiferent ranges depending on the treating steps as hereinafter described.

To illustrate the invention, av hydrocarbon oil is, catalytically cracked by contact with a crackingcatalyst under cracking conditions; The low boiling fractions are removed from the crackedoil and a residual fraction, boiling at least above 350 F., is obtained. This residual fraction contains a substantial quantity of polynuclear aromatic hydrocarbons which are believed to be the desirable components of the inhibitors of the invention. It 18 possible to employ diflierent treating steps, in converting the residual fraction into the'additive of the invention, but

it is essential, in'the dilferent steps, to observe certain critical limitations as described hereinafter.

In an embodiment of the invention,lthe residual fraction from catalytic cracking is agitated with from'0.5 to 5 pounds of concentrated (above B.) sulfuric acid per barrel. After agitation, the acidis separated from the reaction mixture. Preferably acidic components of the oil are neutralized with a base, such as with an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or the like, the relatively strong bases such as those of the alkali metals being preferred. The residual fractionis then distilled to separate a fraction, the components of which have a molecular weight within the range of from about 200 to 400. This latter fraction is'the inhibitor of the invention} tlt .is sometimes' desirable to use a preliminary "distillation :to separate-components within the stated molecular weight range prior to 2,846,372 Patented Au g. 5,1958

acid treatment, but the distillation after acid treatment should also be employed to separate high boiling materials formed in the acid treatment. To illustrate the importance of using a quantity of sulfuric acid within the stated range, it was found that using up to 5 pounds of 66 B. sulfuric acid per barrel of additive gave products that exhibited good results in inhibiting oil oxidation, whereas with larger amounts, poor results were obtained. For example, with pounds of 66 B. sulfuric acid per barrel, additives which increased the rate of oxidation of oils compounded therewith were obtained.

As described above, it is essential that the residual fraction be from an operation involving catalytic cracking, that the quantity of concentrated sulfuric acid employed be within the stated ranges, and that the components of the additives have molecular weights within the stated range.

It is sometimes preferable to concentrate the aromatic constituents of the residual fraction from catalytic cracking prior to treatment with sulfuric acid. This can be accomplished by contacting the fraction boiling above about 350 F. with furfural, sulfur dioxide, silica gel, nitrobenzene, phenols or other extractant selective for separating aromatic hydrocarbons from non-aromatic hydrocarbons. The polynuclear aromatic hydrocarbons are then separated from the extractant and treated as above described. An advantage of concentrating the polynuclear aromatic constituents is that wax, which otherwise would be present in the additive when using a wax-containing crude oil, is removed. Other means of removing wax can be employed where necessary or desirable. When using stock which has been thermally cracked prior to the catalytic cracking, wax does not appear in the bottom fraction used to prepare the additive of the invention.

Another embodiment of the invention involves the distillation of the residual fraction from a catalytic cracked stock in the presence of a strong base, such as an alkali metal hydroxide or alkaline earth metal hydroxide, sodium hydroxide, potassium hydroxide or calcium hydroxide being preferred. It is of advantage in this embodiment to employ a polynuclear aromatic concentrate as above described. It is also of advantage during this distillation to separate the desired components having molecular weights within the range of 200 to 400. To illustrate this embodiment, an aromatic concentrate prepared by separating aromatic constituents from the residual fraction of a catalytically cracked oil is distilled while admixed with from 1% to by weight, and preferably from 2% to 5% by weight, of about 50 B. sodium hydroxide. The concentration of caustic does not appear critical, and other concentrations can be employed, but in general the concentration will be above about B. A fraction containing hydrocarbons hav ing molecular weights within the range of from 200 to 400 is separated and is the inhibitor of the invention.

A stabilizing quantity of the oxidation inhibitor prepared as above described, which can vary from 0.5 to 5% by weight depending on the oil being stabilized, is incorporated in the oil. Smaller amounts do not achieve the desired results and higher quantities may cause the compostion to exhibit an increased tendency for oxidation, as shown by the examples described hereinafter. It is preferred to employ from 0.8 to 3% by weight of the inhibitor, since optimum results are obtained within these limitations. It is also preferred to employ the additive of the invention as the sole oxidation inhibitor in oil compositions since, as has been found, combining other materials heretofore described as oxidation inhibitors therewith does not enhance the oxidation stability of the oil to an extent greater than observed with the additive of the invention used above.

A still further embodiment of the invention is to prepare the composition of the invention'by incorporating in the oil to be stabilized an appropriate quantity, as above defined, of the residual fraction from catalytic cracking having a molecular weight within the range of from about 200 to 400. This compostion is then treated with from 0.1 to 4 pounds per barrel of concentrated sulfuric acid, say above about B. After agitation, the phases are allowed to separate and the acid phase removed. The treated hydrocarbon layer is then treated with from about 4 to 25 pounds of clay per barrel. On separation of the clay, the finished product is obtained. It has been found, however, that clay contacting can be used in the invention only when the additive is incorporated with the oil to be stabilized prior to the acid contacting.

The following examples illustrate the several embodi' ments of the invention. In the examples, interfacial tension, between water and oil, and changes in this interfacial tension, are used to measure oxidation of the oil, ASTM D971-50 being used for this measurement. The oxidation procedure, unless otherwise designated in the examples, was to pass air for 96 hours at the rate of 7 ml. of air (measured at ambient temperature and pressure) per ml. of oil per minute through a ml. oil sample maintained at 200 F. in contact with 25 cm. of iron wire (B. & S. No. 19) and 25 cm. of copper wire (B. & S. No. 18). The actual tensiometer readings, determined by ASTM D971-50, are directly comparable for oils of similar density, such as those of the following examples, and hence the values in the examples given under the columns entitled lnterfacial tension after oxidation, are the tensiometer readings after oxidation, and usually these values are for a blend of oil plus additive, as also indicated in the column title, unless otherwise indicated in the examples. The values given in the columns entitled Difference in interfacial tensions are the differences between the tensiometer reading obtained with oil plus additive and the oil alone, both measured after oxidation for 96 hours at 200 F.

EXAMPLE 1 As above stated, it is essential that the residual fraction from which the oxidation inhibitor of the invention is prepared be from a catalytically cracked oil. This is shown by the present example. Four catalytically cracked and one thermally cracked tower bottoms (all boiling above 350 F.) were examined for activity toward oxidation inhibition. Sources A through D were from catalytic cracking as follows: Source A, from cracking catalytic gas oil over a fixed bed of commercial silica-alumina cracking catalyst; source B, from cracking fresh light gas oil in a moving bed of commercial silica-alumina cracking catalyst; source C, from cracking reduced crude over a' fixed bed of commercial silica-alumina cracking catalyst; source D, from topping and cracking of crude petroleum over a fixed bed of commercial silica-alumina cracking catalyst. Source E was from the thermal cracking of fresh naphtha.

The boiling ranges of the additive fractions employed and data obtained are shown in the following Table I. in each instance 2.5% by weight of the additive from the indicated source was employed. The oil employed was a transformer oil prepared from a hydrocarbon fraction boiling from about 530 F. to 750 F. by contacting with sulfuric acid and subsequently with clay.

As above stated, the values in the column Difference in interfacial tensions were obtained by substracting the interfacial tension of the oil without the additive, determined after oxidation, from the interfacial tenson of the oil with the additive, i; e., of the blend, also determined after oxidation.

. tives;

. obtained are shown in following Table II:

into 2 samples.

be I 1' i [Boiling Interfacial Difierence Source range of tension of in inter- Y additive; blend after facial 7 11. oxidation tensions In this example, the additive components had molecular weights within the range of from 200 to 400. It will be noted that the additive from source E exerted a deleterious effecitfas shown by the negative value obtained for. the

' change in surface tension, which shows'that the oil plus additive was oxidized to an extent greater'than the oil'above. Although stabilization toward oxidation was obtained with the .additives from sources A through D,

ing steps also enhance the stabilizing value ofgthe addi- EXAMPLE 2 of the residual'fractions from catalytic cracking,-fractions from source A and source B of Example 1 were separated into .narrow boiling range fractions, and the narrow fractions tested for oxidation inhibition. Data and results Table II .Boiling Out of Interfacial Difference Range Distillate tension of in Inter-- F.) 1 (Pereenty blendafter facial oxidation Tensions 525-570 10-20 11. 2 -.-0. 570-585 -30 19. 8 7. 585-645 -40 20. 8 8. 645-655 40-50 21.5 9. 655-690 50-60 22. 5 10. 690-710 60-70 .354 23. 710-750 70-80 26. 7 Y '14. 750-820 80-90 1 10.1, 1. r v r 655-690 -56 22.8 v 10. SourceB 690-710 56-62 32.6 20. 1 Q g 710-750 62-77 31.1 19.

.' the molecular weights of the 65'5-690 P. fraction and the 7l0-750 F. fraction, both of source A, were 275 and 320, respectively. Thesevalues are within the preferred molecular weight range of from 25 0 to 350, and good oxidation inhibition was obtained therewith. The molecular weight of the 585-645 P. fraction was about 210, and

the results indicate this to be just above the lower permissible limit. 7 ".ponents'having molecular weights within the stated ranges When using an aromatic extract, the commay boil 'within somewhat different temperature limits than those shown, probably due to an azeotropic effect.

. In the foregoing data, the same diificulty encountered inExamplel' with color formation-was observed. This is overcome as shown in the following examples.

EXAMPLES. V

A residual fraction fromcatalytic cracking was divided Sample 1 'was distilled to separate the fraction shown below in Table III. Sample 2 was dis- .6 tilled from 1% by weight of 50 B. sodium hydroxide. Various quantities of the additives were addedto a transformer oil that had been treated with sulfuric acid and subsequently with clay. NPA color of the blends are shown both-beforeoxidation (initial) and after oxidation (aged). Data andresults. obtained are shown in followingTableIII: 7 h Ta'b'Z 'III Quantity NPA color Interfacial Difference Boiling of tension of in Inter- Sample Range Additive blend after facial (F.) (Wt. oxidation" Tensions Percent) Initial Aged I These data show the improvement in color obtained by distilling from caustic the residualfraction from catalytic cracking, and also that the so-treated fraction is a more effective inhibitortoward-oxidation thanthe comparable fraction from simple distillation, i. e.,-distillation without caustic. Y i 1 EXAMPLE 4- I This example demonstrates the remarkable efiective resistance toward oxidation' exhibited bytheoil compositions of the invention. A residual fraction from catalytic cracking'over a commercial silica-alumina catalyst .was distilled from 2% by weight of 50 B. sodium hydroxide. Components of the resulting-product had a molecular weight of from 250 to350. Various amountsof the additive were incorporated in-a-transformer oil which had been treated with sulfuricacid andsubsequentlywith clay. These compositions wereoxidized according to A ASTM-943; the procedure being modified by using 2% water, instead of 20% water, and by humidifying theoxygen, by bubbling. through water, prior .to passing .it through theoil being tested. In the test; theoil composition is considered to be spent. when theinterfacial tension decreases to 15 dynes/cm. The following Table IV- shoWs the interfacial tensions after various times using oil compositions having the indicated amount of additive. Without any additive, the oil becomes spent Within about 65 hours.

Table IV These data illustrate the remarkably long life of the oil compositions of the invention. The color of the compositions was good throughout the test, NPA colorsof between 4 and 5 being observed.

EXAMPLE 5 '7 An oil boiling in the lubricating oil range was extracted with furfural and subsequently treated with clay. Samples of the resulting oil, the oil with 1% additive, and with 2% additive were oxidized by air at 240 F. in the pics- 7 Table V Interiacial tension Time (hours) additive additive additive EXAMPLE 6 In order to demonstrate the efiect of using various concentrations or" the additive in oil compositions, varying quantities thereof were added to a transformer oil. The additive was prepared from the residue of an oil that had been subjected to thermal cracking and subsequently to catalytic cracking over a commercial silica-alumina cracking catalyst by treating with 3 pounds of 66 B. sulfuric acid per barrel of the fraction, neutralizing with aqueous sodium hydroxide, and distilling components having molecular weights within the range of from 200 to 400. Varying quantities of this additive were added to portions of the transformer oil described in Example 1. Following Table VI shows the data and results obtained:

Table VI Interracial Difierence Color Concentration of additive Tension of in Inter- (Wt. Percent) blend after facial oxidation Tensions NPA NPA96 Initial hours These data show that, with the additive employed, a concentration thereof of about 1% is optimum. The optimum will vary, however, with the particular additive and oil employed. in general, the optimum concentration will be from 0.8% to 3%, but concentrations of from 0.5% to 5% are operative. As shown by the example, use of a relative large quantity of the additive may result in deleterious effects.

The invention claimed is:

1. Method for the preparation of an oxidation inhibitor adapted to impart increased resistance to oxidation to oleaginous materials Which comprises: (A) catalytically cracking a hydrocarbon oil by contact with a cracking catalyst under cracking conditions, (B) separating from the cracked oil a residual fraction boiling above 350 F., (C) contacting said residual fraction with an extractant selective for separating aromatic hydrocarbons from nonaromatic hydrocarbons thereby producing a fraction having a high aromatic hydrocarbon content, (D) contacting the fraction having a high aromatic hydrocarbon content with from 0.5 to 5 pounds of concentrated sulfuric acid per barrel of the fraction contacted, (E) separating acid from the residual fraction, (F) neutralizing acidic components of the separated residual fraction, and (G) distilling the separated residual fraction to separate components thereof having molecular weights within the range of 200 to 400.

2. Method according to claim 1 wherein the sulfuric acid has a concentration of at least 65 B.

3. Method according to claim 2 wherein acid components of the acid-treated fraction are neutralized with an aqueous solution of a strong base.

4. Method for the preparation of an oxidation inhibitor adapted to impart increased resistance to oxidation to oleaginous materials which comprises: (A) catalytically cracking a hydrocarbon oil by contact with a cracking catalyst under cracking conditions, (B) separating from the cracked oil a residual fraction boiling above 350 F., (C) contacting said residual fraction with an extractant selective for separating aromatic hydrocarbons from non-aromatic hydrocarbons thereby producing a fraction having a high aromatic hydrocarbon content, (D) separating from the fraction having a high aromatic content a fraction the components of which have molecular Weights within the range of from 200 to 400, (E) incorporating from 0.5% by weight to 5% by Weight of the last mentioned fraction in a hydrocarbon oil, (F) contacting the resulting composition with from 0.1 to 4 pounds of concentrated sulfuric acid per barrel of the composition, (G) separating sulfuric acid from the treated fraction, (H) contacting the acid-treated fraction with clay, and (I) separating clay from the hydrocarbon product.

5. Method according to claim 4 wherein the sulfuric acid has a concentration equivalent to at least Be.

6. Method for the preparation of an oxidation inhibitor adapted to impart increased resistance to oxidation to oleaginous materials which comprises: (A) catalytically cracking a hydrocarbon oil by contact with a cracking catalyst under cracking conditions, (B) separating from the cracked oil a residual fraction boiling above 350 F., (C) contacting said residual fraction with an extractant selective for separating aromatic hydrocarbons from non-aromatic hydrocarbons thereby producing a fraction having a high aromatic hydrocarbon content, and (D) distilling the high aromatic content fraction in the presence of a minor quantity of a strong base to separate a fraction consisting of components having molecular Weights within the range of from 200 to 400.

7. Method according to claim 6 wherein said strong base is sodium hydroxide.

8. The oxidation inhibitor prepared by the method of claim 1.

9. A new composition of matter comprising an olcaginous material unstable toward oxidation and from 0.5 to 5% by weight of the oxidation inhibitor prepared by the method of claim 1.

10. A new composition of matter comprising a hydrocarbon oil unstable toward oxidation and from 0.5% to 5% by weight of the oxidation inhibitor prepared by the method of claim 1.

11. The oxidation inhibitor prepared by the method of claim 4.

12. A new composition of matter comprising an olcaginous material unstable toward oxidation and from 0.5 to 5% by weight of the oxidation inhibitor prepared by the method of claim 4.

13. Anew composition of matter comprising a hydrocarbon oil unstable toward oxidation and from 0.5 to 5% by weight of the oxidation inhibitor prepared by the method of claim 4.

14. The oxidation inhibitor prepared by the method of claim 6.

15. A new composition of matter comprising an oleaginous material unstable toward oxidation and from 0.5 to 5% by weight of the oxidation inhibitor prepared by the method of claim 6.

16. A new composition of matter comprising a hydro carbon oil unstable toward oxidation and from 0.5% to 5% by weight of the oxidation inhibitor prepared by the method of claim 6.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Reiley Aug. 7, 1951 10 OTHER REFERENCES Brooks et a1.: Chemistry of Petroleum Hydrocarbofis,"

vol. 2, pp. 68 and 69 (1955). (Abstracted/from Meeting Am. Chem. Soc., April 1951, Symposium'on the Chemi- 5 cal Composition of Petroleum, April 1951, p. 105.)

Reinhold Publishing Corp., New York, N, Y. 

1. METHOD FOR THE PREPARATION OF AN OXIDATION INHIBITOR ADAPTED TO IMPART INCREASED RESISTANCE TO OXIDATION TO OLEAGINOUS MATERIALS WHICH COMPRISES: (A) CATALYTICALLY CRACKING A HYDROCARBON OIL BY CONTACT WITH A CRACKING CATALYST UNDER CRACKING CONDITIONS, (B) SEPARATING FROM THE CRACKED OIL A RESIDUAL FRACTION BOILING ABOVE 350*F., (C) CONTACTING SAID RESIDUAL FRACTION WITH AN EXTRACTANT SELECTIVE FOR SEPARATING AROMATIC HYDROCARBONS FROM NONAROMATIC HYDROCARBONS THEREBY PRODUCING A FRACTION HAVING A HIGH AROMATIC HYDROCARBON CONTENT, (D) CONTACTING THE FRACTION HAVING A HIGH AROMATIC HYDROCARBON CONTENT WITH FROM 0.5 TO 5 POUNDS OF CONCENTRATED SULFURIC ACID PER BARREL OF THE FRACTION CONTACTED, (E) SEPARATING ACID FROM THE RESIDUAL FRACTION, (F) NEUTRALIZING ACIDIC COMPONENTS OF THE SEPARATED RESIDUAL FRACTION, AND (G) DISTILLING THE SEPARATED RESIDUAL FRACTION TO SEPARATE COMPONENTS THEREOF HAVING MOLECULAR WEIGHTS WITHIN THE RANGE OF 200 TO
 400. 8. THE OXIDATION INHIBITOR PREPARED BY THE METHOD OF CLAIM
 1. 